A sensor is a device that is designed to detect changes in a quantity (i.e., a measurand) and provide a corresponding output. All-optical, fiber-coupled sensors have many advantages over many other conventional sensors (e.g., acoustic sensors, etc.), such as small size and weight, ability to operate in chemically and/or electrically harsh environments, ease of multiplexing large numbers of sensors, and compatibility with fiber-optic networks for data transport and processing. They are therefore attractive for use in many applications.
Such sensor networks often rely upon fiber-Bragg grating (“FBG”) sensors to measure a measurand (e.g., temperature and/or strain). It is relatively easy to integrate multiple FBG sensors in a single-fiber network because each sensor has only a limited number of operating wavelengths. Prior-art FBG sensor systems usually employ swept-wavelength sources so that all of the sensors in the network can be interrogated by a single source. Although easy to implement, the dynamic range of a typical FBG sensor is relatively poor and this has limited their deployment in many applications.
Fabry-Perot (“FP”) cavity-based sensors are often used in applications in which the limitations of FBG sensors are not easily overcome. FP sensors are widely used, for example, in many optical-sensor-based accelerometer and pressure sensing applications. But FP sensors are not without their own limitations. For instance, it is challenging to multiplex FP sensors in a single-fiber network because of inter-sensor interference.
An optical-sensor based network that has high dynamic range and is easily implemented would provide an attractive alternative to sensor networks known in the prior art.